Access line management in a memory device
Memory devices and methods are disclosed, such as devices configured to store a number of access line biasing patterns to be applied during a memory device operation performed on a particular row of memory cells in the memory device. Memory devices are further configured to support modification of the stored bias patterns, providing flexibility in biasing access lines through changes to the bias patterns stored in the memory device. Methods and devices further facilitate performing memory device operations under multiple biasing conditions to evaluate and characterize the memory device by adjustment of the stored bias patterns without requiring an associated hardware change to the memory device.
1. A memory device, comprising:
an array of memory cells;
a first register associated with an access line that can be used to selectively access the array;
a second register associated with the access line;
a plurality of voltage sources; and
driver circuitry configured to couple the access line to a respective one of a plurality of voltage sources responsive to first bias information stored in the first register when the memory device is in a first mode of operation; and
wherein the driver circuitry is further configured to couple the access line to a respective one of the plurality of voltage sources responsive to second bias information stored in the second register when the memory device is in a second mode of operation; and
wherein the first bias information is determined using the second mode of operation.
2. The memory device of claim 1 , wherein the memory device is further configured to perform a memory device operation on the array after the first bias information is stored in the first register and/or the second bias information is stored in the second register.
3. The memory device of claim 2 , wherein the memory device is further configured to perform the memory device operation after the access line is coupled to one or more of the plurality of voltage sources.
4. The memory device of claim 1 , wherein the first bias information and the second bias information each comprises a respective voltage source selection.
5. The memory device of claim 1 , wherein the driver circuitry comprises a decoder, wherein the decoder is configured to couple the access line to one or more of the voltage sources responsive to the stored first bias information and/or the stored second bias information.
6. The memory device of claim 1 , further comprising control circuitry configured to operate the memory device in one of the first mode and the second mode of operation responsive to a mode indication received at an interface of the memory device.
7. The memory device of claim 1 , wherein the array of memory cells comprises an array of NAND configured flash memory cells.
8. The memory device of claim 1 , wherein the first mode of operation is a user mode of operation and the second mode of operation is a test mode of operation.
9. The memory device of claim 1 , wherein the plurality of voltage sources comprises a plurality of separate voltage sources.
10. The memory device of claim 1 , wherein the plurality of voltage sources provide an incrementally increasing voltage.
11. The memory device of claim 1 , wherein there is a step change in voltage between each voltage source of the plurality of voltage sources.
12. The memory device of claim 1 , wherein the driver circuitry comprises respective ones of a plurality of transistors respectively coupled to respective ones of the plurality of voltage sources.
13. The memory device of claim 12 , wherein the driver circuitry comprises a decoder coupled to control gates of the respective ones of the plurality of transistors.
14. The memory device of claim 13 , further comprising a multiplexer that selectively couples the first register and the second register to the driver circuitry.
15. The memory device of claim 1 , further comprising control circuitry configured to access locations in the array of memory cells storing the second bias information and to load the second bias information into the second register.
16. The memory device of claim 15 , wherein the control circuitry is configured to access the locations in the array of memory cells storing the second bias information and to load the second bias information into the second register upon initialization of the memory device.
17. The memory device of claim 15 , wherein the control circuitry is configured to access the locations in the array of memory cells storing the second bias information and to load the second bias information into the second register in response to a command from a host.
18. The memory device of claim 1 , wherein the access line comprises a global access line commonly coupled to a plurality of string drivers, wherein respective ones of the plurality of string drivers are respectively coupled to respective ones of a plurality of blocks of memory cells of the array of memory cells.
19. The memory device of claim 18 , wherein the respective ones of the plurality of string drivers are to respectively receive different enable signals.